Kinetic distribution of spirochetes in tissues of mice. BALB/c mice were sacrificed at various time points after infection. The brain, heart, liver and spleen tissues were tested for Borrelia by qPCR. (A): B. burgdorferi B31 and (B): B. garinii SZ. The mean numbers of spirochetes per 106 mouse cells (calculated on the basis ofβ-actin standard curves) are given.